Jig for guiding placement of femoral component of the implant in knee replacement surgery

ABSTRACT

The present jig for guiding placement of femoral component of the implant in a knee replacement surgery (J) is a pre-assembled Jig (J) that ensures precision fit femoral implant for knee replacement based on difference of cuts in millimeters instead of the usual angle measurement in degrees. It avoids intrusion of the intramedullary canal substantially decreasing the risks of embolism. It enables the surgeon to use precise values of depth of cuts obtained from a system for obtaining optimum fit implant as described in patent application number 3896/MUM2015. This enables the surgeon to control precisely the placement of the implant in terms of flexion or extension, varus or valgus, internal or external rotation. It also enables precise placement of the four-in-one cutting block simultaneously with the distal femur cut; ensuring precise placement of knee femoral component of the knee implant. This reduces efforts and time taken during surgery.

CROSS REFERENCE TO RELATED APPLICATIONS

This is the U.S. National Stage of International Application No.PCT/IN2017/050297, filed Jul. 19, 2017, which was published in Englishunder PCT Article 21(2), which in turn claims the benefit of IndiaApplication No. 201721018055, filed May 23, 2017, which is incorporatedherein by reference in its entirety.

FIELD OF INVENTION

The present invention relates to a jig for guiding a femoral componentof knee replacement. In particular, present invention relates to amodular jig which is pre-assembled to ensure precision fit femoralimplant for knee replacement based on difference of cuts in millimetersinstead of the usual angle measurement in degrees. It avoids intrusionof the intramedullary canal substantially decreasing the risks ofembolism. It enables the surgeon to use precise values of depth of cutsobtained from a system for obtaining optimum fit implant as described inpatent application number 3896/MUM2015. This enables the surgeon tocontrol precisely the placement of the implant in terms of flexion orextension, varus or valgus, internal or external rotation It alsoenables precise placement of the four-in-one cutting blocksimultaneously with the distal femur cut; ensuring precise placement ofknee femoral component of the knee implant. This reduces efforts andtime taken during the surgery.

BACKGROUND OF THE INVENTION

The knee joint is made up of three bones: femur, tibia and patella. Kneereplacement surgery (arthroplasty) is usually necessary when thecartilage covering the three bones of the knee joint (viz., femur, tibiaand patella) is worn or damaged to the extent that one's mobility isreduced and one experience pain even while resting. Replacing thedamaged knee joint with an optimum fit artificial implant in an optimumposition and alignment can help reduce pain and increase mobility.

X-rays are used as standard investigation and planning tools for kneereplacement surgeries wherein a single ‘snapshot’ of a body part istaken. It provides a two dimensional image of bone for analysis.However, they fail to determine the deformities at certain parts of thebones or between the bones. X-rays also show deformities in varyingdegrees of magnification. Thus, accurate measurement of the deformitiesin millimeters cannot be assured using X-rays. The guiding instruments(jigs) used for performing knee replacement were based on observationsfrom X-rays. To overcome the inadequacies of the two dimensionalinvestigation tool like X-ray and magnification errors, the deformitiesare calculated as angles in degrees. Hence, standard guiding instrumentsto place the implant in proper position and alignment allowed forchanges in degrees.

The X-rays are unable to render a three dimensional surfacerepresentation and hence, the standard jigs for the femur bone werereferenced of the intramedullary canal in the femur. A hole is made inthe end of the femur bone in the knee. A rod is inserted in the femur.And a jig is mounted on the rod at an angle. This angle is eitherdecided arbitrarily by the surgeon or based on the X-ray measurements ofangles in degrees between the intramedullary canal axis and the desiredmechanical axis of the femur. Besides, the rotation of the jig isuncontrolled and hence the angle is taken in any undefined plane.

Nam D et al published in Journal of Arthroplasty, 2016 September issue,pages 91-6 on comparison of use of a fixed arbitrary angle versusvariable distal femur resection angle based on X-rays. They concludedthat the use of a variable distal femur resection angle improves femoralcomponent alignment after total knee arthroplasty. Maderbacher G et alpublished in the journal of Knee Surgery Sports Traumatology Arthroscopyin May 2016 issue on “What is the optimal valgus pre-set forintramedullary femoral alignment rods in total knee arthroplasty?” Theyconcluded that exact component alignment could not be achieved and theX-ray measurements were inadequate.

Insertion of rods in the intramedullary canal of the femur during totalknee replacement is also associated with higher risk of embolism(pushing fat and blood globules from the canal into the blood streamwhich can damage the lungs and heart). Malhotra R et al published in theAmerican issue of Journal of Bone and Joint Surgery, June 2015, pages889-94 regarding the embolic load during total knee replacement surgerywith intramedullary rod. It was found to be higher.

Maderbacher G et al published in journal of Knee Surgery SportsTraumatolgy Arthroscopy in the August 2016 issue, pages 2453-60, on“Appropriate sagittal femoral component alignment cannot be ensured byintramedullary alignment rods.” They concluded that intramedullaryalignment rods do not ensure a distal cutting block alignment between 0to 3 degrees of flexion in relation to femoral mechanical axis. Theextent of flexion or extension could not be foreseen by the surgeon.

Kucukdurmaz F et published in the Journal of Surgery TechnologyInternational, November 2015 issue, pages 225-32 on “Do StandardSurgical Guides Produce Accurate and Precise Femoral Bone Resectionsduring Total Knee Arthroplasty?” They found that none of the threeexisting instrumentation systems that they tested were within 1 mm ofthe desired cut resection. Only 30-40% cases were within 2 mm of thedesired cut resection with these systems. They concluded thatimprovements in instrumentation are warranted to increase accuracy andprecision.

With the development of technology, Computerized Tomography (CT) scanand Magnetic Resonance Imaging (MRI) scan which are being increasinglyused as tools to better understand the diseases/deformities related toknee. CT Scans can reproduce accurate three-dimensional models of thebones with precise surface rendering.

Patient specific jigs uses either pre-operative CT or MRI scans. But, inabsence of a tool directly in the hands of a surgeon to plan surgery,the actual surgery is planned by a biomedical engineer sitting in afaraway country. The entire process is controlled by the implantmanufacturer through the biomedical engineer, and hence a single designknee is only considered while planning. The biomedical engineer pickslandmark positioning based on his skills and local biases. Thus, for thepatient, his surgery is planned by a biomedical engineer who would havehis limitations and would not be performing the surgery. The operatingsurgeon is only given the final plan for approval. A patient specificJig is then 3D printed, sterilized and dispatched to the operatingsurgeon. After the surgery, this jig has to be discarded as it wasspecific only for this patient. Thus, there are huge time delays andincremental costs, leading the method into disrepute and lack ofwidespread use. Hence, reusable, modular, universal instrumentationbased on these investigations is needed.

Majority of the surgeons have popularly started using CT Scans and MRIsfor diagnosis of deformities. There were no means to analyze and find anoptimum fit implant and its optimum position and alignment. The presentinventor has developed a system for analyzing and guiding to find anoptimum fit implant and its optimum position and alignment for a kneereplacement surgery as described in patent application number3896/MUM2015. However, instrumentation based on these investigations isneeded to guide precise placement of femoral component of the kneeimplant while doing a knee replacement surgery.

PRIOR ART

Various jig based systems for assisting knee replacement surgeries havebeen applied for patents are disclosed in different patent documents:

U.S. Pat. No. 5,624,444 discloses a set of instruments and method foruse in knee replacement surgery, specifically to make the necessaryfemoral resections is described. The simplified set of instrumentsallows the necessary femoral resections to be performed with fewerinstruments, and with fewer necessary steps for the surge onto take. Theset of instruments includes a three-dimensional jig which references theanterior and posterior femoral condyles to allow determinations as toalignment, placement, and prosthesis size before any bone cuts are made.However, it depends on angles in degrees based on X-ray measurements. Itcompels the surgeon to place the implant in the axis of theintramedullary rod in the lateral view and the surgeon cannot flex orextend the implant.

U.S. Pat. No. 4,474,177 discloses a method and apparatus for preparingthe distal surface of a femur to receive a distal femoral prosthesisemploying an intramedullary reamer which is used to internally locatethe central long axis of the femur, an intramedullary alignment guidewhich is inserted into the space left in the intramedullary canal uponremoval of the reamer and at least one femoral surface modifyinginstrument which cooperatively engages with a guide handle attached tothe intramedullary alignment guide to accomplish the shaping of thedistal femoral surface. However, it depends on angles in degrees basedon X-ray measurements. It compels the surgeon to place the implant inthe axis of the intramedullary rod in the lateral view and the surgeoncannot flex or extend the implant.

U.S. Pat. No. 8,221,430 discloses a method a method of manufacturing anarthroplasty jig from CT scans or MRI scans. A 3D model is generatedfrom the CT scan or MRI scan. The surface model is generated and patientspecific jig is contoured on the bone surface. These jigs can then bemanufactured. However, these jigs can be used for that specific patientonly and have to be discarded. There would be time delays between CTscan and manufacturing of the jig and there would be incremental costs.

DISADVANTAGES OF THE PRIOR ART

Various jig based systems available for assisting the knee replacementare available. However, they suffer from at least one of the followingdisadvantages:

-   -   They fail to provide precision in placement of femoral component        of the implant on the femur in terms of position and alignment;        in a knee replacement surgery.    -   Generally followed protocols of knee replacement surgeries that        work on two dimensions; wherein the rotation of the jig is        uncontrolled and hence the angle is taken in any undefined        plane; whereby they fail to attain the precision in three        dimensions.    -   Generally followed protocols of knee replacement surgeries        violates medullary canal and thereby generates the high risk of        embolism.    -   Many of the jigs are complicated to use yet fail to effectively        aid in knee replacement surgery to attain precision in implant        placement.    -   Separate jigs are required for the steps of sizing and that of        distal cut to be taken one after the other; making the knee        replacement surgery time consuming; which in-turn requires the        knee to be kept open for a longer time substantially increasing        the chances of infection.    -   The available sets of jigs fail to minimize the bone loss.    -   There are multiple instrumentation for doing of multiple tasks        of sizing and distal cuts, thereby increasing number of        instruments to be prepared and sterilized. Thus there is        increased spending of resources in terms of energy inputs and        labor.    -   They lack in accuracy.    -   They are not reliable.    -   They fail to facilitate the doctor to work with acumen.    -   They fail to aid the knee replacement surgery that can in turn        provide Patient satisfaction.

OBJECTIVES OF THE INVENTION

The main objective of the present invention is to provide jig forguiding placement of femoral component of the implant in a kneereplacement surgery that enables to attain precision in placement offemoral component of the implant on the femur in terms of position andalignment; wherein said precision is attained in three dimensions incontrast to the generally followed protocols of knee replacementsurgeries that work on two dimensions.

Another objective of the present invention is to provide jig for guidingplacement of femoral component of the implant in a knee replacementsurgery avoids intrusion of the intramedullary canal substantiallydecreasing the risks of embolism.

Yet another objective of the present invention is to provide jig forguiding placement of femoral component of the implant in a kneereplacement surgery that is simple to use yet effectively aids kneereplacement surgery to attain precision in implant placement.

Yet another objective of the present invention is to provide jig forguiding placement of femoral component of the implant in a kneereplacement surgery whereby both the steps of sizing and that of distalcut are taken care at same time; making the knee replacement surgeryless time consuming; which in-turn requires the knee to be kept open fora lesser time substantially decreasing the chances of infection.

Another objective of the present invention is to provide jig for guidingplacement of femoral component of the implant in a knee replacementsurgery with precision in three dimensions to help minimize the boneloss.

Yet another objective of the present invention is to provide jig forguiding placement of femoral component of the implant in a kneereplacement surgery which enables doing of multiple tasks of sizing anddistal cuts together, thereby reducing number of instruments to beprepared and sterilized, saving resources in terms of energy inputs andlabor.

Yet another objective of the present invention is to provide a jig forguiding placement of femoral component of the implant in a kneereplacement surgery which is highly accurate.

Yet another objective of the present invention is to provide a jig forguiding placement of femoral component of the implant in a kneereplacement surgery which is reliable.

Yet another objective of the present invention is to provide a jig forguiding placement of femoral component of the implant in a kneereplacement surgery which facilitates the doctor to work with acumen.

Yet another objective of the present invention is to provide jig forguiding placement of femoral component of the implant in a kneereplacement surgery which aids in knee replacement surgery to enhancePatient satisfaction.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1-1 Shows fragmented view of present jig for guiding placement offemoral component of the implant in a knee replacement surgery FIG. 1.2Shows perspective front view of present jig for guiding placement offemoral component of the implant in a knee replacement surgery FIG. 1.3Shows perspective back view of present jig for guiding placement offemoral component of the implant in a knee replacement surgery FIG. 1.4Shows axial view of present jig for guiding placement of femoralcomponent of the implant in a knee replacement surgery; highlightingcontact five points and illustrating rotation control. FIG. 1.5 Showscoronal view of present jig for guiding placement of femoral componentof the implant in a knee replacement surgery; illustrating varus-valguscontrol. FIG. 1.6 Shows sagittal view of present jig for guidingplacement of and FIG. femoral component of the implant in a kneereplacement 1.7 surgery; illustrating flexion-extension control. FIG.2.1 Shows fragmented view of the first embodiment of present jig forguiding placement of femoral component of the implant in a kneereplacement surgery FIG. 2.2 Shows perspective front view of the firstembodiment of present jig for guiding placement of femoral component ofthe implant in a knee replacement surgery FIG. 2.3 Shows perspectiveback view of the first embodiment of present jig for guiding placementof femoral component of the implant in a knee replacement surgery FIG.2.4 Shows axial view of the first embodiment of present jig for guidingplacement of femoral component of the implant in a knee replacementsurgery; highlighting contact five points and illustrating rotationcontrol. FIG. 2.5 Shows coronal view of the first embodiment of presentjig for guiding placement of femoral component of the implant in a kneereplacement surgery; illustrating varus-valgus control. FIG. 2.6 Showssagittal view of the first embodiment of present jig and FIG. forguiding placement of femoral component of the implant 2.7 in a kneereplacement surgery; illustrating flexion-extension control. FIG. 3.1Shows fragmented view of the second embodiment of present jig forguiding placement of femoral component of the implant in a kneereplacement surgery FIG. 3.2 Shows perspective front view of the secondembodiment of present jig for guiding placement of femoral component ofthe implant in a knee replacement surgery FIG. 3.3 Shows perspectiveback view of the second embodiment of present jig for guiding placementof femoral component of the implant in a knee replacement surgery FIG.3.4 Shows axial view of the second embodiment of present jig for guidingplacement of femoral component of the implant in a knee replacementsurgery; highlighting five contact points and illustrating rotationcontrol. FIG. 3.5 Shows coronal view of the second embodiment of presentjig for guiding placement of femoral component of the implant in a kneereplacement surgery; illustrating varus- valgus control. FIG. 3.6 Showssagittal view of the second embodiment of present and FIG. jig forguiding placement of femoral component of the 3.7 implant in a kneereplacement surgery; illustrating flexion- extension control. FIG. 4.1,Illustrates the third embodiment of the present jig for FIG. 4.2 guidingplacement of femoral component of the implant in and FIG. a kneereplacement surgery. 4.3

Wherein:

Meaning of Reference numerals of said component parts of presentinvention:

J Present jig for guiding placement of femoral component of the implantin a knee replacement surgery or present Jig. PP Posterior paddles PPSPosterior slots for bushings (in Posterior paddles) PBU PosteriorBushing DB Distal block DBS Distal slots for bushings (in Distal block)DBM Distal slots for marking DBU Distal bushing DBB Distal block forbushing DMB Distal Marking block AP Anterior probe with adjustableheight PB Probe MC Measuring cylinder SMC slots for placing measuringcylinder LB Locking bolt AB Anterior cutting block (for cutting distalfemur) SL Slot for saw blade HO Holes h1 First height h2 Second heightMLP medio-lateral probes

Additional References (not the Part of Present Jig)

P1 Distal lateral condyle P2 Distal medial condyle P3 Posterior lateralcondyle P4 Posterior medial condyle and P5 Distal anterior cortex

SUMMARY OF THE INVENTION

Referring to FIGS. 1.1 to 1.7, 2.1 to 2.7 and 3.1 to 3.7; the presentjig for guiding placement of femoral component of the implant in a kneereplacement surgery (J) mainly comprises of:

-   -   Posterior paddles (PP)    -   Posterior slots for bushings (in Posterior paddles) (PPS)    -   Posterior Bushing (PBU)    -   Distal block (DB)    -   Distal slots for bushings (in Distal block) (DBS)    -   Distal bushing (DBU)    -   Distal slot for marking (DBM),    -   Distal block for bushing (DBB),    -   Distal Marking block (DMB),    -   Supporting Block (SB),    -   Plurality of holes (DHO),    -   Pair of stems (PS),    -   Slots for measuring cylinder (SMC),    -   Anterior probe with adjustable height (AP),    -   Probe (PB),    -   Measuring cylinder (MC),    -   Locking bolt (LB),    -   Anterior cutting block (for cutting distal femur) (AB),    -   Slot for saw blade (SL),    -   Holes (HO).

The present jig (J) uses measurements of displacement of Jig (J) ofdistal femur of the bone, in a knee replacement surgery; wherein, toachieve precise cut as per the values of depth of cuts obtained from asystem for obtaining optimum fit implant as described in presentapplicant's another patent application, numbered as 3896/MUM2015.

This is to ensure precise position and alignment of the implant on thecut bone so as to achieve minimum bone loss and maximum patientsatisfaction. While using the said obtained values, the present Jig (J)is used to obtain precise cuts on the distal femur in a knee replacementsurgery. This requires precise placement of present Jig (J) on thedistal femur in all three planes to enable precise cuts on the bone.This precise placement is ensured by the precisely measured (inmillimeters) bushings used to create rotations in different plane. Saidrotations are controlled by the present Jig (J) as under:

-   -   Rotation in axial plane: internal and external rotations are        controlled by displacement of the posterior bushings (PBU) in 1        mm increment on the Posterior paddles (PP). (FIG. 1.4, 2.4, 3.4)    -   Similarly, rotations in coronal plane: varus or valgus are        controlled by displacement of distal bushing (DBU) in 1 mm        increment on the distal block (DB). (FIG. 1.5, 2.5, 3.5)    -   The rotations in the sagittal plane: flexion or extension are        controlled by displacement in 1 mm increment on the anterior        probe (AP). This is measured displacement of probe (PB) in the        measuring cylinder (MC). (FIG. 1.6, 1.7, 2.6, 2.7, 3.6, 3.7)

Thus, the present Jig (J) uses measurements in millimeters (mm) in allthree planes instead of the generally used angles in degrees (Referprior art) in an undefined plane.

When the present Jig (J) is placed on the distal femur, it comes incontact with the bone at different points. The points are termed hereinafter as contact points. Said contact points are used as referencepoints to take precise measurements while adjusting the Jig to preciseposition so as to take precise cuts. Said contact points are preferablyfive or more than five to achieve the precise adjustments ofmeasurement.

Present description embodies five such contact points while achievingprecise position and alignment of the present Jig (J) on the distalfemur:

P1: Distal lateral condyle,

P2: Distal medial condyle,

P3: Posterior lateral condyle,

P4: Posterior medial condyle and

P5: distal anterior cortex.

These five points defines the five degrees of freedom:

(1) Internal and external rotation (rotation in axial plane) iscontrolled by points of contact on posterior medial condyle andposterior lateral condyle (P3 and P4) as shown in the FIGS. 1.4, 2.4 and3.4.

(2) Varus and valgus (rotation in coronal plane) is controlled by pointsof contact on distal medial condyle and distal lateral condyle (P1 andP2) as shown in the FIGS. 1.5, 2.5 and 3.5.

(3) Flexion and extension (Rotation in sagittal plane) is controlled bypoints of contact on posterior medial condyle, posterior lateral condyleand anterior cortex (P3, P4 and P5), (refer FIGS. 1.6, 1.7, 2.6, 2.7,3.6 and 3.7)

(4) Distal translation (Depth of cut, translation in axial plane) iscontrolled by points of contact on distal medial condyle and distallateral condyle (P2 and P1) and

(5) Antero-posterior translation (translation in sagittal plane) iscontrolled by points of contact on posterior medial condyle, posteriorlateral condyle and distal anterior cortex (P4, P3 and P5).

DESCRIPTION OF THE INVENTION

The present invention embodies a jig for guiding placement of femoralcomponent of the implant in a knee replacement surgery (J). The presentJig (J) allows precise distal femoral cut with sizing and marking forsubsequent femoral anterior, posterior and chamfer cuts simultaneously,saving surgery time. The present Jig (J) enables placement of thefemoral component in all three planes with precision without violatingthe intramedullary canal. The present jig (J) is pre-assembled to ensureprecision fit femoral implant for knee replacement based on differenceof cuts in millimeters instead of the usual angle measurement indegrees.

The main embodiment of the present invention embodies a jig for guidingplacement of femoral component of the implant in a knee replacementsurgery (J) that mainly comprises of:

-   -   Posterior paddles (PP),    -   Posterior slots for bushings (PPS),    -   Posterior Bushing (PBU),    -   Distal block (DB),    -   Distal slots for bushings (DBS),    -   Distal bushing (DBU),    -   Anterior probe with adjustable height (AP),    -   Probe (PB),    -   Measuring cylinder (MC),    -   Locking bolt (LB),    -   Anterior cutting block (for cutting distal femur) (AB),    -   Slot for saw blade (SL),    -   Holes (HO).

Referring to FIGS. 1.1 to 1.7; shows the present jig for guidingplacement of femoral component of the implant in a knee replacementsurgery (J). Said Jig (J) has a pair of Posterior paddles (PP) madepreferably of metal and having posterior slots (PPS) to accept posteriorbushings (PBU). Said Jig (J) is placed on distal femur (for which kneereplacement surgery is being done) such that said pair of Posteriorpaddles (PP) touches the posterior medial (P4) and posterior lateral(P3) femoral condyle as shown in FIG. 1.4, 2.4, 3.4, 1.6, 1.7, 2.6, 2.7,3.6, 3.7. The points of contact (P4 and P3) on the posterior medial andposterior lateral femoral condyles represent the posterior condylar axis(see FIG. 1.4). The precise rotation (internal or external rotation) ofthe femoral component is determined by rotating the femoral componentaxis by rotating the present Jig (J) further posteriorly from the pointof contact (posterior condylar axis) on either the lateral or medialposterior femur (P3 and P4) with the help of a bushing (PBU) of 1 mmincrement. The amount of rotation (internal or external rotation) ismeasured by the offset required in form of the bushing (PBU) on theposterior medial or posterior lateral (P4 or P3) paddles in millimetersinstead of degrees.

Further, a Distal block (DB) is provided with a pair of Distal slots forbushings (DBS) for accepting Distal bushing (DBU). Said Distal block(DB) is a continuous metal sheet at right angles to the Posteriorpaddles (PP). Said Distal block (DB) is to be placed over the distalmedial (P2) and distal lateral femur (P1)(FIG. 1.5, 2.5, 3.5). Thepoints of contact on the distal medial and distal lateral femoralcondyles (P2 and P1) represent the distal femoral axis. The preciserotation (varus or valgus) of the femoral component is determined byrotating the femoral component axis by rotating the jig further mediallyor laterally from the point of contact on either the lateral or medialdistal femoral condyle with the help of a bushing of 1 mm increment. Theamount of rotation is measured by the offset required in form of thebushing on the distal block in millimeters instead of degrees.

Anterior probe with adjustable height (AP) having a sliding adjustableprobe (PB) is provided wherein said probe (PB) is of variable height offthe distal block (DB). It represents a fixed distance from the posteriorpaddles (PP) which are in continuation with the distal block (DB). Ithas a Measuring cylinder (MC) which is attached to said distal block(DB) through Locking bolt (LB). The distance between the tip of theanterior probe (PB) to the bushing on the posterior paddles (PP)represents the antero-posterior size of the femoral component (h1, h2)(refer FIG. 1.6, 1.7, 2.6, 2.7, 3.6, 3.7). The femoral component isplaced in flexion by decreasing the antero-posterior distance.Similarly, the femoral component is placed in extension by increasingthe antero-posterior distance. The size of the femoral component is alsodetermined by the antero-posterior distance.

Thus, the present jig for guiding placement of femoral component of theimplant in a knee replacement surgery (J) enables precise alignment andpositioning of the femoral component in three dimensions by enablingprecise adjustments of rotations in all three dimensions.

An anterior cutting block (for cutting distal femur) (AB) is alsoprovided with Slot for saw blade (SL). This is a detachable block madepreferably of metal attached to the distal block (DB). Once therotations in all three dimensions are finalized and the jig (J) isplaced with decided rotations, the distal femur cut is taken through theslot (SL) on this block (AB). Said anterior cutting block (AB) has holes(HO) to increase the depth of the distal femoral cut by 1, 2, or 3 mm.

OTHER EMBODIMENTS OF THE INVENTION

The present invention embodies other three major embodiments. Theseembodiments allow for simultaneous marking for the subsequent Jig forsubsequent cuts of the femur, namely anterior posterior and chamfers.Thus, there is an additional provision in said embodiments to providesaid markings through Distal Slots for marking (DBM). Said slots (DBM)are either placed on the same distal block (DB) along with slots forbushing (DBS) (as shown and described in first embodiment) or are placedas separate distal blocks (DBB and DMB as shown and described in secondembodiment). Said embodiments are described herein below:

I. The First Embodiment

The jig for guiding placement of femoral component of the implant in aknee replacement surgery (J) of the first embodiment mainly comprisesof:

-   -   Posterior paddles (PP),    -   Posterior slots for bushings (PPS),    -   Posterior Bushing (PBU),    -   Distal block (DB),    -   Distal slots for bushings (DBS),    -   Distal slot for marking (DBM),    -   Supporting block (SB),    -   plurality of holes (DHO),    -   pair of stems (PS),    -   Distal bushing (DBU),    -   Anterior probe with adjustable height (AP),    -   Probe (PB),    -   Measuring cylinder (MC),    -   Slots for measuring cylinder (SMC),    -   Locking bolt (LB),    -   Anterior cutting block (for cutting distal femur) (AB),    -   Slot for saw blade (SL),    -   Holes (HO).

The first embodiment (refer FIGS. 2.1 to 2.7) provides separable distalblock (DB) which is separable from said posterior paddles (PP) withslots (PPS) for posterior bushings (PBU); wherein said Distal Block (DB)is attached to posterior paddles (PP) through plurality of holes (DHO)on lower portion of the distal block (DB) for accepting the pair ofstems (PS) protruding out of the supporting block (SB) connected to theposterior paddles (PP). Said plurality of holes (DHO) are so arranged asto enable fixing of the distal block (DB) at different heights from theposterior paddles (PP). Said different heights are preferably 0, 1 mm, 2mm, and 3 mm. Said height is determined by half the distance of theheight of the bushing (PBU) placed on the posterior paddle (PP). Thisprovision enables the marking for subsequent Jig at a pre-determinedheight from the posterior paddles (PP).

Further, said first embodiment involves the Distal slots for bushings(DBS) and Distal slots for marking (DBM) in same and continuous Distalblock (DB). Distal bushings (DBU) are used in controlling the rotationsare described herein above, by placing them in said slots for bushings(DBS). Further, marking Bushings available from the implant company areused to mark for the subsequent Jig through said Distal slots formarking (DBM).

Anterior probe with adjustable height (AP) having a sliding adjustableprobe (PB) is provided wherein said probe (PB) is of variable height offthe distal block (DB). It represents a fixed distance from the posteriorpaddles (PP) which are in continuation with the distal block (DB). Ithas a Measuring cylinder (MC) which is attached to said distal block(DB) through Locking bolt (LB). The distance between the tip of theanterior probe (PB) to the bushing on the posterior paddles (PP)represents the antero-posterior size of the femoral component (h1, h2)(refer FIG. 2.6, 2.7). The femoral component is placed in flexion bydecreasing the antero-posterior distance. Similarly, the femoralcomponent is placed in extension by increasing the antero-posteriordistance. The size of the femoral component is also determined by theantero-posterior distance.

Additionally, said embodiment provides plurality of slots for placingmeasuring cylinder (SMC) wherein said slots (SMC) are used to place themeasuring cylinder (MC) at different heights so as to decrease theworking length of the anterior probe (PB). Anterior cutting block (AB)is attached at a fixed height on the distal block (DB).

An anterior cutting block (for cutting distal femur) (AB) is alsoprovided with Slot for saw blade (SL). This is a detachable block madepreferably of metal attached to the distal block (DB). Once therotations in all three dimensions are finalized and the jig (J) isplaced with decided rotations, the distal femur cut is taken through theslot (SL) on this block (AB). Said anterior cutting block (AB) has holes(HO) to increase the depth of the distal femoral cut by 1, 2, or 3 mm.

II. The Second Embodiment

The second embodiment (refer FIGS. 3.1 to 3.7) provides a jig forguiding placement of femoral component of the implant in a kneereplacement surgery (J) which comprises of:

-   -   Posterior paddles (PP),    -   Posterior slots for bushings (PPS),    -   Posterior Bushing (PBU),    -   Distal block for bushing (DBB),    -   Distal slots for bushings (DBS),    -   Distal Marking block (DMB),    -   Distal slot for marking (DBM),    -   Distal bushing (DBU),    -   Anterior probe with adjustable height (AP),    -   Probe (PB),    -   Measuring cylinder (MC),    -   Locking bolt (LB),    -   Anterior cutting block (for cutting distal femur) (AB),    -   Slot for saw blade (SL),    -   Holes (HO).

Said Jig (J) has said pair of posterior paddles (PP) connected at rightangles to the Distal Block for Bushing (DBB). Said Block (DBB) hasdistal slots for bushing (DBS) for accepting the distal bushings (DBS).The distal slots for marking (DBM) are provided on a separate blocknamely distal marking block (DMB). Anterior probe with adjustable height(AP) has said measuring cylinder (MC), which is attached to said DistalBlock for Bushing (DBB). The distal marking block (DMB) slides on themeasuring cylinder (MC). Said marking block (DBM) is fixed at apre-determined height on said measuring cylinder (MC) through a lockingbolt (LB). The anterior probe (PB) is also fixed to the distal markingblock (DMB). Thus, the measurement on the measuring cylinder (MC)reflects the height (h1, h2) (refer FIG. 3.6, 3.7) from the tip of theprobe (PB) to the bushing (PBU) on the posterior paddles (PP). TheAnterior cutting block (AB) is attached at a fixed height on the distalmarking block (DMB).

III. The Third Embodiment

The third embodiment provides a pair of medio-lateral probes (MLP) to beplaced on distal block (DB) or the Distal block for bushing (DBB) ordistal marking block (DMB) of the embodiments described herein above.The probes (MLP) define the sixth degree of freedom. They controlmedio-lateral placement of the implant (translation in the coronalplane). Thus, all six degrees of freedom are controlled by saidembodiment. (FIG. 4)

Having described what is considered the best form presently contemplatedfor embodying the present invention, various alterations, modifications,and/or alternative applications of the invention for any system will bepromptly apparent to those skilled in the art. Therefore, it is to beunderstood that the present invention is not limited to the practicalaspects of the actual preferred embodiments hereby described and thatany such modifications and variations must be considered as being withinthe spirit and the scope of the invention, as described in the abovedescription.

WORKING OF THE INVENTION

The analysis for optimum fit implant and its optimum position is derivedfrom the system for obtaining optimum fit implant as described in patentapplication number 3896/MUM2015 or a similar system. The depth of cutson the distal femur and posterior femur along with the antero-posteriordistance is obtained from the said system. These are used to calculatethe placement and the size of the bushings.

-   -   For the distal bushings: The difference in the depth of cuts on        distal medial and distal lateral femur gives the size of the        bushing (DBU) to be used on the distal femur. The bushing is        placed on the smaller cut side in terms of medial or lateral        placement on the distal femur.    -   For the posterior bushings: Similarly, the difference in the        depth of cuts on posterior medial and posterior lateral femur        gives the size of the bushing (PBU) to be used on the posterior        femur. The bushing (PBU) is placed on the smaller cut side in        terms of medial or lateral placement on the posterior femur.    -   The antero-posterior distance gives the height of the anterior        probe to be adjusted in the measuring cylinder (MC).

From the said data, the bushings of the desired size are placed first onthe medial or lateral distal block and posterior paddles (PP). Theheight of the anterior probe (PB) is adjusted according to theantero-posterior distance derived from the said system. The probe isattached to the distal block (DB). The assembled jig (J) is placed onthe femur ensuring contact at the following five points: (1) posteriorpaddle with or without the bushing on posterior-medial condyle, (2)posterior paddle with or without the bushing on the posterior lateralcondyle, (3) distal block with or without the bushing on distal medialcondyle, (4) distal block with or without the bushing on distal lateralcondyle and (5) tip of anterior probe on the anterior cortex. Theanterior distal cutting block is then, fixed to the femur with pins. Theremaining jig is then removed. The distal femoral cut is checkedclinically to assess the cuts. It has the additional option of +/−2,+/−4 mm or +/−6 mm cut for increasing or decreasing the depth of thedistal femur resection.

In first embodiment of the jig, besides the above steps, another bushingof the desired size of the implant as provided by the implant company isplaced in the slots in the distal block with slots for markingsubsequent femur cuts. The placement of the subsequent jig is markedwith a drill or a pin. The distal anterior cutting block is left inplace and the remaining jig is detached and removed. The distal femoralcut is made after clinically assessing the depth. It has the additionaloption of +/−2, +/−4 mm or +/−6 mm cut for increasing or decreasing thedepth of the distal femur resection.

In the second embodiment of the jig, besides the first steps detailedabove, the placement of the subsequent jig is marked directly throughthe holes provided in the block with slots for marking subsequent femurcuts.

The slot on the anterior distal cutting block is then, used to take thedistal femur cut.

Example 1

For patient A, LQS from implant company ZIN was the optimum implantderived by using the system for obtaining optimum fit implant asdescribed in patent application number 3896/MUM2015 or a similar system.The values derived were implant size D, the distal femoral cuts were 9mm on the medial side and 7 mm on the lateral side. The posterior cutswere 8 mm on the medial side and 6 mm on the lateral side. As companyZIN was selected, the jig (J) of the first embodiment was used. Thus, a2 mm bushing was used on the lateral side distally (9−7=2 and smallerside was lateral) and another 2 mm bushing was used on the lateral sideposteriorly (8−6=2 and smaller side was lateral). The anterior heightgiven was 48 mm. the probe (PB) was fixed at 48 mm. The assembly wasplaced at distal femur ensuring the five point contact. The distalanterior cutting block was fixed with 2 pins. The remaining jig wasremoved and the distal cut was taken through the slot in the distalanterior cutting block.

COMPANY GENERIC Distal cut only Pat Lat Med Bush Bush Lat Med Bush BushAnt No. Dist Dist Dist side Post Post Dist side Dist Probe 1 8 7 1 Med 79 2 Med 48 48 2 10 8 2 Med 8 10 2 Med 53 53 3 9 6 3 Med 8 10 2 Med 59 594 9 10 1 Lat 7 9 2 Med 46 46 5 8 10 2 Lat 6 8 2 Med 49 49 6 9 9 0 0 8 102 Med 55 55 7 8 9 1 Lat 6 10 3 Med 54 54 8 6 8 2 Lat 7 9 2 Med 51 51 9 911 2 Lat 6 10 4 Med 52 52 10 8 8 0 0 9 11 2 Med 64 64

Example 2

For patient A, NRX from implant company STY was the optimum implantderived by using the system for obtaining optimum fit implant asdescribed in patent application number 3896/MUM2015 or a similar system.The values derived were implant size 7, the distal femoral cuts were 9mm on the medial side and 7 mm on the lateral side. The posterior cutswere 8 mm on the medial side and 6 mm on the lateral side. As companySTY was selected, the jig (J) of the first embodiment was used. Thus, a2 mm bushing was used on the lateral side distally (9−7=2 and smallerside was lateral) and another 2 mm bushing was used on the lateral sideposteriorly (8−6=2 and smaller side was lateral). The anterior heightgiven was 53 mm. The posterior paddles (PP) were attached at 1 mm as theposterior bushing was 2 mm. The probe (PB) was attached in the slots forplacing measuring cylinder (SMC) of 45 mm and placed at 7 mm because 1mm was already covered by shifting the distal block by 1 mm. Theassembly was placed at distal femur ensuring the five point contact. Thesize 7 bushing from company STY was placed in the distal slot formarking (DBM). The distal anterior cutting block was fixed with 2 pins.The subsequent Jig placement was marked by drilling through the companybushing placed in the distal block for marking (DBM). The remaining jigwas removed and the distal cut was taken through the slot in the distalanterior cutting block. This was then removed and the size 7 cuttingblock from STY was placed to complete the femoral cuts.

Similar examples are shown in the table attached below:

COMPANY STY Pat Lat Med Bush Bush Lat Med Bush Bush Ant Post Comp No.Dist Dist Dist Side Post Post Dist side Dist Padd Slot Probe Bush 1 8 71 Med 7 9 2 Med 48 1 45 2 5 2 10 8 2 Med 8 10 2 Med 53 1 45 7 7 3 9 6 3Med 8 10 2 Med 59 1 55 3 9 4 9 10 1 Lat 7 9 2 Med 46 1 45 0 4 5 8 10 2Lat 6 8 2 Med 49 1 45 3 6 6 9 9 0 0 8 10 2 Med 55 1 45 9 8 7 8 9 1 Lat 610 3 Med 54 1 45 8 8 8 6 8 2 Lat 7 9 2 Med 51 1 45 5 7 9 9 11 2 Lat 6 104 Med 52 2 45 6 7 10 8 8 0 0 9 11 2 Med 64 1 55 8 11

Example 3

For patient B, DES from implant company MER was the optimum implantderived by using the system for obtaining optimum fit implant asdescribed in patent application number 3896/MUM2015 or a similar system.The values derived were implant size D, the distal femoral cuts were 8mm on the medial side and 10 mm on the lateral side. The posterior cutswere 9 mm on the medial side and 6 mm on the lateral side. As companyMER was selected, the jig (J) of the second embodiment was used. Thus, a2 mm bushing was used on the medial side distally (10−8=2 and smallerside was medial) and another 3 mm bushing was used on the lateral sideposteriorly (9−6=3 and smaller side was lateral). The anterior heightgiven was 55 mm. The probe (PB) was locked at 55 mm with the help of thelocking bolt. The assembly was placed at distal femur ensuring the fivepoint contact. The distal anterior cutting block was fixed with 2 pins.The subsequent Jig placement was marked by drilling through the companybushing placed in the distal block for marking (DBM). The remaining jigwas removed and the distal cut was taken through the slot in the distalanterior cutting block. This was then removed and the size D cuttingblock from MER was placed to complete the femoral cuts.

Similar examples are shown in the table attached below.

COMPANY MER Pat Lat Med Bush Bush Lat Med Bush Bush Ant No. Dist DistDist side Post Post Dist side Dist Probe 1 8 7 1 Med 7 9 2 Med 48 48 210 8 2 Med 8 10 2 Med 53 53 3 9 6 3 Med 8 10 2 Med 59 59 4 9 10 1 Lat 79 2 Med 46 46 5 8 10 2 Lat 6 8 2 Med 49 49 6 9 9 0 0 8 10 2 Med 55 55 78 9 1 Lat 6 10 3 Med 54 54 8 6 8 2 Lat 7 9 2 Med 51 51 9 9 11 2 Lat 6 104 Med 52 52 10 8 8 0 0 9 11 2 Med 64 64

FIG. 1.5 shows angle A1. FIG. 2.4 shows angle A2. FIG. 2.5 shows angleA3. FIG. 3.4 shows angle A4. FIG. 3.5 shows angle A5.

The invention claimed is:
 1. A jig for guiding placement of femoralcomponent of the implant in a knee replacement surgery (J) mainlycomprises of: Posterior paddles (PP), Posterior slots for bushings (inPosterior paddles) (PPS), Posterior Bushing (PBU), Distal block (DB),Distal slots for bushings (in Distal block) (DBS), Distal bushing (DBU),Anterior probe with adjustable height (AP), Probe (PB), Measuringcylinder (MC), Locking bolt (LB), Anterior cutting block (for cuttingdistal femur) (AB), Slot for saw blade (SL), Holes (HO); Said Jig (J)has a pair of Posterior paddles (PP) made preferably of metal and havingposterior slots (PPS) to accept posterior bushings (PBU); said pair ofPosterior paddles (PP) touches the posterior medial (P4) and posteriorlateral (P3) femoral condyle while placing present jig (J) on distalfemur wherein present jig (J) rotated posteriorly from the point ofcontact (posterior condylar axis) on either the lateral or medialposterior femur (P3 and P4) with the help of a bushing (PBU) of 1 mmincrement to achieve precise rotation; said Distal block (DB) isprovided with a pair of Distal slots for bushings (DBS) for acceptingDistal bushing (DBU) wherein said Distal block (DB) is a continuousmetal sheet at right angles to the Posterior paddles (PP); said Distalblock (DB) touches distal medial (P2) and distal lateral femur (P1)while it be Jig (J) is placed on the distal femur wherein the presentjig (J) is rotated medially or laterally from the point of contact oneither the lateral or medial distal femoral condyle with the help of abushing (DBU) of 1 mm increment to achieve precision; said anteriorprobe with adjustable height (AP) having a sliding adjustable probe (PB)is provided wherein said probe (PB) is of variable height off the distalblock (DB); it has a Measuring cylinder (MC) which is attached to saiddistal block (DB) through Locking bolt (LB); wherein the femoralcomponent is placed in flexion by decreasing the antero-posteriordistance; similarly, the femoral component is placed in extension byincreasing the antero-posterior distance; an anterior cutting block (forcutting distal femur) (AB) is also provided with Slot for saw blade (SL)for taking femur cuts; this is a detachable block (AB) made preferablyof metal attached to the distal block (DB); said anterior cutting block(AB) has holes (HO) to increase the depth of the distal femoral cut by1, 2, or 3 mm.
 2. The present jig for guiding placement of femoralcomponent of the implant in a knee replacement surgery (J) as claimed inclaim 1, wherein the amount of rotation (internal or external rotation)is measured by the offset required in form of the bushing (PBU) on theposterior medial or posterior lateral (P4 or P3) paddles in millimetersinstead of degrees.
 3. A jig for guiding placement of femoral componentof the implant in a knee replacement surgery (J) comprising of:Posterior paddles (PP), Posterior slots for bushings (PPS), PosteriorBushing (PBU), Distal block for bushing (DBB), Distal slots for bushings(DBS), Distal Marking block (DMB), Distal slot for marking (DBM), Distalbushing (DBU), Anterior probe with adjustable height (AP), Probe (PB),Measuring cylinder (MC), Locking bolt (LB), Anterior cutting block (forcutting distal femur) (AB), Slot for saw blade (SL), Holes (HO); SaidJig (J) has said pair of posterior paddles (PP) connected at rightangles to the Distal Block for Bushing (DBB) and said Block (DBB) hasdistal slots for bushing (DBS) and the distal slots for marking (DBM)are provided on a separate block namely distal marking block (DMB); themeasuring cylinder (MC) is attached to said Distal Block for Bushing(DBB) and the distal marking block (DMB) slides on the measuringcylinder (MC) wherein Said marking block (DBM) is fixed at apre-determined height on said measuring cylinder (MC) through a lockingbolt (LB); further, the anterior probe (PB) is also fixed to the distalmarking block (DMB); the Anterior cutting block (AB) is attached at afixed height on the distal marking block (DMB).
 4. A jig for guidingplacement of femoral component of the implant in a knee replacementsurgery (J) as claimed in claim 3; having a pair of medio-lateral probes(MLP) to be placed on distal block (DB) or the Distal block for bushing(DBB) or distal marking block (DMB).
 5. The present jig for guidingplacement of femoral component of the implant in a knee replacementsurgery (J) as claimed in claim 3, wherein the amount of rotation(internal or external rotation) is measured by the offset required inform of the bushing (PBU) on the posterior medial or posterior lateral(P4 or P3) paddles in millimeters instead of degrees.